Convolute drive spring



Dec. 6, 1960 R. L. ZOERB CONVOLUTE' DRIVE SPRING Filed Sept. 25, 1958 RALEIGH L. ZOERB INVENTO/P HUE'BNER & WORREL ATTORNEYS CONVOLUTE DRIVE SPRING Raleigh L. Zoerb, 3745 El Monte Way, Fresno, Calif asslgnor, by mesne assignments, of one-half to Alice M. Zoerb, Fresno, Calif.

Filed Sept. 25, 1958, Ser. No. 763,294

6 Claims. (Cl. 267-1) The present invention relates to a convolute drive spring for a spring motor and more particularly to an improved spring of this type in which crystallization and breakage incident to winding and unwinding of the spring are minimized.

For the purpose of more fully understanding the contribution of the present invention to the practical art, reference is preliminarily made to some of the problems of the prior art minimized or obviated by the present invention. Spring motors of the type usually found in clocks, typewriters, adding machines, and the like, generally employ a spiral spring fitted in a housing, having an inner end fixedly anchored in any suitable manner, and an outer end on the outermost convolution adapted to be engaged by a finger inwardly extended from the housing. The housing is mounted for rotation relative to the fixed inner end of the spring and is intended, as a result of such rotation, to wind the spring into a relatively contracted condition. Escapement means, and the like, are usually provided for controlled release of the housing to reclaim energy stored in the spring incident to winding. Such structure is typified by the carriage take-up spring on typewriters.

More specifically, the subject invention is concerned with the connection of any suitable driven means, such as the finger on the housing, with the outermost convolution of the spring. In the past, conventional springs of this type have provided the outermost convolution with an eyelet adjacent to its terminal end. This eyelet receives the described finger. During winding of the spring by rotation of the housing, the finger engages the outermost spiral adjacent to its terminal end and pulls the spirals of the spring in a winding direction placing the same under tension. During unwinding operations, the finger is drawn by the spring and the portion thereof adjacent to the eyelet likewise placed under tension. Since the application of winding and unwinding forces are frequently sudden, vigorous and repetitive, fatigue of the metal adjacent to the eyelet rwults. Because of the location of the eyelet closely adjacent to the terminal end of the outermost spiral, and because of the usually relatively narrow width of the spirals, said terminal ends have been found unable long to withstand the stresses and strains imparted thereto incident to use. It has been found that this is one of the most commonly occurring failures in typewriters, clocks, watches and other machines employing this type of spring Repair usually requires replacement of the broken spring.

Accordingly, it is an object of the present invention to provide an. improved convolute spring of the type em- 'ilnited States atent stresses and strains in the relatively weaker portions of the spring.

Another object is to increase the life of convolute drive springs of the character described.

Another object is to minimize the expense and inconvenience associated with the rapair and maintenance of machines or devices employing convolute springs motivating or actuating springs.

Another object is to impart strength and durability to a convolute spring without changing the material or gauge thereof.

These, together with other objects and advantages, will become more fully apparent upon reference to the following description.

In the drawing:

Fig. 1 is a transverse cross section taken through a spring motor employing a convolute spring which embodies the principles of the present invention.

Fig. 2 is a somewhat enlarged axial section taken on a plane having the position represented by line 2-2 of Fig. 1.

Fig. 3 is a still further enlarged fragmentary transverse section showing in particular the improvement of the present invention.

Fig. 4 is a fragmentary, enlarged, face view of the device of the present invention showing in dashed line the outer end and end connection of a convolute drive spring employed therein.

Referring more particularly to the drawing, aspring motor of the type discussed adapted for use in typewriters, adding machines, timepieces, and the like, is generally indicated in Fig. l by the numeral 10'. The motor includes a housing 11 having a substantially cylindrical, annular side Wall 12 providing an inwardly disposed surface 13 and an outwardly disposed surface 14. The side wall is concentric to an axis for the housing, and a pair of annular, axially spaced, circumscribing flanges 16 are radially outwardly extended from the outer surface of the side wall to provide a circumscribing channel.

The housing 11 also includes an end wall 20 inwardly extended from the side wall 12 and providing an annular hub 21 concentric to the axis of the housing. A roller bearing 22 is fitted in the hub and is adapted to mount the housing for rotatable movement in a manner to be described.

A support arm 25 is fragmentarily illustrated in Fig. 2 and includes a mounting stud 26 providing a socket screw threadably receiving an axle bolt 27. The bearing 22 is fitted on the stud so as to mount the housing 11 for rotatable movement concentrically of its axis, the latter being coaxial with the bolt 27 A hub ring 35 is positioned on the bolt 27 between the head thereof and the stud 26. The ring is held in fixed position against the stud 26 by tightening the bolt into the socket. A spiral or convolute drive spring 38, incorporating the principles of the present invention, includes an inner end 39 connected to the ring 35 by means of an anchor pin 40, a plurality of spirals or convolutions 41 wound around the inner end and the ring in a predetermined direction, clockwise as viewed in Fig. 1, and including an outermost convolution 42. The outermost convolution is adjacent to the inwardly disposed surface 13 of the side wall 12 and provides a substantially U- shaped outer end portion 43. This end portion further includes a main section 45' and a reversely curved or turned section 46 bent backwardly from the main section and between the main section and the inwardly disposed surface 13 of the side wall, all as best seen in Fig. 3, and terminating in an end edge 46'. The U-shaped end portion also provides a smoothly curved intermediate bend 47 joining the main and reversely curved sections. The reversely curved section terminates in a bifurcated terminal end providing a notch 48 opening endwardly of the reversely curved section and oppositely disposed from the direction of outward spiral progression of the spring. The notch is defined by an inner edge 49 disposed transversely of the reversely curved section and being longitudinally spaced intermediate the end edge 46' and the intermediate bend 47. Actually, the inner edge is relatively closely adjacent to said end edge while being relatively remotely spaced from said bend. The side wall 12 of the housing 11 has a winding finger 52 struck inwardly therefrom and fitted into the notch in the spring so as to bear against the reversely curved section upon rotation of the housing in the same direction as the spirals of the spring are wound around the inner end of the spring, namely, clockwise as viewed in Fig. 1.

An elongated flexible Winding strap 56 includes an end 57 connected to the outwardly disposedsurface 14 of the side wall 12 of the housing 11 between the flanges 16 by means of a pin 58, and an opposite manipulating end 59. The strap will be recognized as the carriage return strap of a typewriter and typifies means for winding the spring and receiving stored energy therefrom.

Operation The operation of the described embodiment of the subject invention is believed to be readily apparent and is briefly summarized at this point.

Whenever the spring 38 is to be wound, the manipulating end 59 of the winding strap 56 is pulled in a direction indicated by arrow 65. This rotates the housing 11 in a clockwise direction, as viewed in Figs. 1 and 3. This being the same direction in which the spirals of the spring are wound around the inner end 39 of the spring. The finger 52 bears against the reversely curved section 46 of the outermost convolution 42 thereby to wind the spirals of the spring around its inner end which is fixedly connected to the stud 46 by means of the ring 35 and the bolt 27.

It is significant to note that the reversely curved section 46 is placed under compression by the finger 52 bearing thereagainst. This is in contrast to the prior art structure wherein the terminal end of the spring is placed under tension. Further, the stresses and strains imparted to the spring by the finger are distributed around the U- shaped end portion 43 and are not concentrated in the terminal end of the outermost convolution 42. The U- shaped outer end portion also functions as a resilient cushion to protect the remainder of the spring especially at the beginning of the pull when winding is initiated by absorbing the force needed to overcome the inertia of the spring rather than transmitting it to the remainder of the spring.

In tests with commercial embodiments of the subject invention, it has been found that the improvement of the present invention minimizes spring fatigue, reduces crystallization and breakage of convolute springs of the character described and actually multiplies the effective life of such springs. The subject invention effectively minimizes the expenses and inconvenience normally incurred in breakdowns, repair, and maintenance of equipment and devices employing convolute drive springs.

Although the invention has been herein shown and described in what is conceived to be the most practical and. preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

.1. In a relatively fixed support, a housing having an. annular side Wall providing an inwardly disposed surface circumscribing an axis of rotation for the housing, means,

mounting the housing on the support for rotation in a predetermined direction about said axis, the housing including a coupling member rigidly inwardly extended from the inner surface of the side wall, a spring adapted to be connected to the coupling member in a manner which minimizes breakage of the spring as the result of stresses and strains imparted to the spring incident to rotation of the housing in said predetermined direction comprising an inner end rigidly connected to the support, and a plurality of convolutions wound around the inner end in said predetermined direction, there being an outermost convolution providing a generally U-shaped reversely turned end portion having an intermediate bent portion, a main portion extended toward said bent portion in said predetermined direction and a reversely turned portion extended from the bent portion in a direction opposite to said predetermined direction and being in outwardly opposed relation to said main portion, the reversely turned portion terminating in an end edge spaced longitudinally along the reversely turned portion from said bent portion, said reversely turned portion providing a notch extended inwardly from said end edge with the notch being defined, by an inner edge in longitudinally spaced relation to said bent portion, and the coupling member being extended into the notch and bearing against said inner edge incident to rotation of the housing in said predetermined direction.

2. In a spring motor including a support; a housing having a substantially cylindrical annular side wall circumscribing an axis for the housing and providing inwardly and outwardly disposed surfaces; means mounting the housing for rotatable movement on the support concentrically of its axis; means connected to the outer surface of the side wall of the housing for applying force substantially tangentially relative to the housing for rotating the housing in a predetermined direction of rotation; a spiral spring having an inner end connected to the support and a plurality of convolutions wound in said predetermined direction around the inner end and outwardly of said axis, there being an outermost convolution terminating in a substantially U-shaped end portion including an inner section, an intermediate bend, and an outer reversely curved section in outwardly opposed relation to the inner section, the outer section providing a bifurcated end including a notch opening endwardly of the reversely curved section, the notch being defined by an inner edge longitudinally spaced along said outer section from the bend; and a coupling finger rigidly inwardly extended from the inner surface of the side wall of the housing and into the notch in said reversely curved section and engaging said inner edge of the notch in spaced relation to said bend during rotation of the housing in said predetermined direction thereby to Wind the spring in said predetermined direction, the stresses and strains imparted to the spring incident to hearing of the finger against said outer section being distributed throughout the U-shaped end portion.

3. In a spring motor; a convolute spring having an inner end, said spring being spirally coiled in a predetermined direction around the inner end and providing an outermost convolution terminating in an elongated U-shaped outer end portion, said outer end portion including opposed main and reversely extended sections interconnected by an intermediate section of smooth curvature, said main section being extended as a part of the outermost convolution in said predetermined direction toward said intermediate section, the reversely extended section being extended from said intermediate section outwardly of the main section and in a direction opposite to said predetermined direction, said reversely extended section terminating in an end edge spaced longitudinally along said reversely extended section from said intermediate section, the reversely extended section having a notch extended from said end edge longitudinally inwardly toward said intermediate section, the notch having an inner edge closely adjacent to said end edge and relatively remotely spaced from said intermediate section, said notch opening outwardly from said end edge; means holding the inner end portion of the spring; and a finger fitted into the notch and bearing against said inner edge for winding the spring in said predetermined direction around the inner end of the spring by movement relative to the holding means in said direction whereby initial force required to overcome the inertia of the spring is absorbed by said U-shaped end portion and whereby the reversely extended section between the intermediate and said inner edge is placed under compression incident to said winding of the spring, there being an open space between said main and reversely extended sections at the intermediate section at all times to accommodate flexing of said intermediate section.

4. In a spring motor, an inner member, an outer member, means mounting said members for relative rotary motion of one thereof with respect to the other about a predetermined axis, a spiral spring having an inner end connected to the inner member and a plurality of convolutions wound in a predetermined direction around said axis and outwardly thereof, said spring having an outermost convolution terminating in a substantially U-shaped end portion including an inner section continuous with the outermost convolution, an intermediate bend continuous with the inner section, and an outer section continuous with the intermediate bend and extended therefrom in a direction opposite to said predetermined direction in outwardly spaced relation to the inner section, and means interconnecting the outer member and the outer section of the spring in driving-driven relation at a position on the outer section in spaced relation to the bend in said predetermined direction therefrom.

5. In a spring motor, an inner member, an outer member, means mounting said members for relative rotary motion of one thereof with respect to the other about a predetermined axis, a spiral spring having an inner end connected to the inner member and a plurality of convolutions wound in a predetermined direction around said axis and outwardly thereof, said spring being disposed in a plane substantially normal to the axis of rotation and having an outermost convolution terminating in a substantially U-shaped end portion including an inner section continuous with the outermost convolution, an intermediate bend continuous with the inner section, and an outer section continuous with the intermediate bend and extended therefrom in a direction opposite to said predetermined direction in outwardly substantially uniformly spaced relation to the outermost convolution, and means interconnecting the outer member and the outer section of the spring in driving-driven relation at a position on the outer section in spaced relation to the bend in said predetermined direction therefrom.

6. In a spring motor including a support; a housing having a substantially cylindrical annular side wall circumscn'bing an axis for the housing and providing inwardly and outwardly disposed surf-aces; means mounting the housing for rotatable movement on the support concentrically of its axis; means connected to the outer surface of the side wall of the housing for applying force substantially tangentially relative to the housing for rotating the housing in a predetermined direction of rotation; a spiral spring having an inner end connected to the support and a plurality of convolutions wound in said predetermined direction around the axis and outwardly therefrom, there being an outermost convolution terminating in a substantially U-shaped end portion including an inner section continuous with the outermost convolution, an intermediate bend continuous with the inner section, and an outer section continuous with the intermediate bend and extended therefrom in a direction opposite to said predetermined direction in outwardly spaced relation to the inner section; and means inwardly extended from the inner surface of the side wall of the housing interconnecting the housing and the outer section of the spring in driving-driven relation at a position on the outer section in spaced relation to the bend in said predetermined direction from the bend.

References Cited in the file of this patent UNITED STATES PATENTS 1,495,348 Odom May 27, 1924 1,699,964 Green Jan. 22, 1929 1,720,289 Odom July 9, 1929 2,797,435 Decker July 2, 1957 

